Question regarding osmotic pressure?

A solution is prepared by dissolving 59.5 g of the water-soluble polymer A in enough water to make 0.97 L of solution. The osmotic pressure of the solution is measured to be 18.4 mmHg at 28.0 �C. Calculate the molar m of polymer A. R = 0.08206 L�atm/mol�K; 1 atm = 760 mmHg.